如何在 Java 中实现基于线程的 UDP 服务器?
How can I implement a threaded UDP based server in Java ?
Basically what I want, is to connect multiple clients to the server, and let each client have his own thread. The only problem is, that I don't know how to check if a client is trying to connect to the server and spawn a new thread for it.
boolean listening = true;
System.out.println("Server started.");
while (listening)
new ServerThread().start();
In this case the server will spawn new threads until it runs out of memory. Here's the code for the ServerThread ( I think I need here a mechanism that stalls the creation of the ServerThread until a client tries to connect.
public ServerThread(String name) throws IOException
{
super(name);
socket = new DatagramSocket();
}
So fathers of Java programming please help.
解决方案The design for this to a certain extent depends on whether each complete UDP "dialog" just requires a single request and immediate response, whether it's a single request or response with retransmissions, or whether there'll be a need to process lots of packets for each client.
The RADIUS server I wrote had the single request + retransmit model and spawned a thread for each incoming packet.
As each DatagramPacket
was received it was passed to a new thread, and then that thread was responsible for sending back the response. This was because the computation and database accesses involved in generating each response could take a relatively long time and it's easier to spawn a thread than to have some other mechanism to handle new packets that arrive whilst old packets are still being processed.
public class Server implements Runnable {
public void run() {
while (true) {
DatagramPacket packet = socket.receive();
new Thread(new Responder(socket, packet)).start();
}
}
}
public class Responder implements Runnable {
Socket socket = null;
DatagramPacket packet = null;
public Responder(Socket socket, DatagramPacket packet) {
this.socket = socket;
this.packet = packet;
}
public void run() {
byte[] data = makeResponse(); // code not shown
DatagramPacket response = new DatagramPacket(data, data.length,
packet.getAddress(), packet.getPort());
socket.send(response);
}
}
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